The Streptomyces silicium strain was mutated on the Shenzhou-9 spacecraft，and the molecular biological characteristics of the mutant strain were analyzed and studied. The effect on increasing yield and improving quality of cotton under the condition of reducing chemical fertilizer combined with the application of bio-organic fertilizer prepared by the strain was verified by field experiment. The results showed that:(1)The diameters of the inhibition zones against Bacillus subtilis for the first and second generations of the mutant strains were 0.76 and 0.81cm，respectively，and the diameters of the inhibition zones for Fusarium oxysporum were 0.69 and 0.72 cm，respectively；The diameters of the inhibition zone of the 1st and 2nd generations of CK strains against Bacillus subtilis were 0.75 and 0.78 cm，respectively，and the diameters of the inhibition zones against Fusarium oxysporum were 0.65 and 0.67 cm，respectively. The antibacterial abilities of Gram-positive bacteria(Bacillus subtilis)and fungi(Fusarium oxysporum)were slightly improved after passage，but the overall difference was not significant，indicating that the mutant strains had better antibacterial genetic stability.(2)The content of active ingredients in the strains was detected，and it was found that both gibberellin A3(GA3)and indoleacetic acid(IAA)were contained in the mutant strains and CK strains，and the contents of GA3 in CK strain and mutant strain were 0.090% and 0.099%，respectively，and the contents of IAA were 0.793% and 0.508%，respectively，which showed that the mutant strain had a dual effect of stimulating crop growth.(3)By reducing the amount of fertilizer and increasing the application of different bio-organic fertilizers，compared with the conventional fertilization of the control treatment，the effect of increasing cotton yield was different. The T1，T2，T3 and T4 treatments increased the yield by 219，748，338 and 83 kg/hm²，respectively，compared with the control treatment，among which T2 treatment(reduced chemical fertilizer by 90 kg/hm² and applied 750 kg/hm² of space biological organic fertilizer)had the most significant increase in yield，with an increase rate of 24.15%；In terms of cotton quality indicators，T2 treatment was also better than other treatments，the fiber length was 35.38 mm，the strength was 35.60 GPT，the uniformity was 90.90%，and the elongation was 6.53%，which had the best performance on cotton quality. The combined application of bio-organic fertilizer and chemical fertilizer prepared by the carrying mutant strain improved the soil，and significantly increased the yield and quality of cotton.